In the broad field of analytical instruments, gas and liquid chromatographs have been used to separate and measure the concentration of the constituents of complex mixtures generally termed samples. In liquid chromatography, a sample is injected into a column having a liquid therein consisting of one or more liquid solvents. A detector at the base of the column detects the presence of the constituents as they appear or elute from the bottom of the column. A plot of the detector output as a function of time, known as a chromatogram, is used by the chromatographer in his analysis of the sample.
For example, it may be desired to know the concentration of a given medication in the blood stream of a patient. A known volume of blood would be entered into a chromatographic column and the constituent parts including the drug fraction would then separate out and be detected. The chromatogram would indicate the concentration of each component. From knowledge of when the medication should separate out, the therapeutic drug level of the medication can be determined. From that, the percentage of medication in the blood can be calculated.
In manually operated instruments a user selects each specimen to be tested one at a time in the desired order, with periodic or intermittent selection of a standard specimen for calibration. The routine is tedious and prone to error, particularly since it is easy for the user to forget to carry out the calibration in the proper order.
Automatic sampling of specimens in a predetermined order with a microprocessor has come into use, such as with a Perkin-Elmer Auto Sampler, solving some of the above-mentioned problems. However state-of-the-art systems still require an operator to place specimen vessels in the receptacle in careful order that matches the selection order of the programmed automatic sampler. A separate calibration specimen must be positioned at periodic positions according to the selected calibration frequency. Flexibility is lacking for making changes in specimens or for preprogramming a procedure change, such as in type of calibration, to occur during a run of tests.
Therefore an object of the present invention is to provide a chromatographic instrument having improved automation of operation.
A more particular object is to provide an improved chromatographic instrument in which an operator places test specimens and a standard specimen in randomly designated locations, and enters procedural information including an ordered list of location information and a preselected calibration frequency, such that the instrument self-generates a set of command instruction lines and effects measurements and computations sequenced according to the ordered list, with at least one calibration command instruction line interspersed therein according to the calibration frequency.
Another object is to provide a chromatographic instrument including a novel command sequence program for generating command instruction lines.
A further object is to provide an improved liquid chromatographic instrument having the above-described features.